Cooling system for an internal combustion engine



H. KOSOFF Aug. 9, 1966 COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE 2 Sheets-Sheet 1 Original Filed June 27, 1963 09 k 5 mm INVENTOR.

HAROLD KOSOFF ATTORNEY 350m moo ll ufi awmm EPE Aug. 9, 1966 H. KOSOFF 3,255,049

COOLING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE Original Filed June 27, 1963 2 Sheets-Sheet 2 INVENTOR.

HAROLD KOSOFF ATTORNEY Unitcd States Patent 3,265,049 COOLING SYSTEM FOR AN INTERNAL CGMBUSTION ENGINE Harold Kosoii, 1203 Hale St., Philadelphia, Pa. Original application June 27, 1963, Ser. No. 291,067, now Patent No. 3,175,584, dated Mar. 30, 1965. Divided and this application Mar. 15, 1965, Ser. No. 442,230

- 6 Claims. (Cl. 12341.35)

This application is a division of my co-pending application Serial No. 291,067, filed June 27, 1963, now U.S. Patent No. 3,175,584.

This invention relates to an internal combustion engine of the type having a number of reciprocating pistons. In particular, it relates to, and has great utility, in free piston engines.

In my-U.S. Patent 3,127,881, granted Apr. 7, 1964, and in my US. Patent 3,129,878, granted Apr. 21, 1964, I described and claimed a new free piston engine having relatively few main parts and free from any mechanical synchronizing linkage between the pistons thereof. While that engine was, in general, highly satisfactory, it became apparent that it was possible to build an even more sophisticated and better engine which incorporated novel features.

It is therefore among the objects of this invention to provide:

('1) An internal combustion engine which includes means therein for minimizing the frictional losses of the pistons.

(2) An internal combustion engine with novel means for providing internal cooling.

(3) An internal combustion engine in which the crankcase and/or compressor chamber are effectively isolated from the combustion chamber.

(4) An internal combustion engine which employs a novel, simple, and highly eflicient compressor intake valve.

(5) An internal combustion engine with novel means for providing internal lubrication.

(6) A free piston engine with novel means for metering the fuel applied thereto.

(7) A free piston engine having novel cooling, lubricating and valve structures.

Other objects of the invention will occur to those skilled in the art upon perusal of the drawings, specification and claims herein.

In accordance with my invention I minimize frictional losses and thereby increase engine efiiciency by reducing the surface area of contact of the pistons with the inner walls of the cylinder. I do this by undercutting the pistons, i.-e., by making selected positions of them have smaller diameters than other portions thereof. In addition, 'I take advantage of this undercut portion by using it as a channel to which external air is applied under pressure for keeping down the temperature of the engine. This air also has the effect of removing any undesired combustion products that get by the rings and thus prevent other regions of the engine from becoming contaminated. Also, I use the changes in the air supply pressure caused by the piston head periodically blocking the air flow as a means for sensing the extent of outward piston stroke. Furthermore, instead of using conventional compressor intake valves that require a pressure differential to activate them, I employ a valve member, disposed around and actuated by the piston, which cooperates with an opening in the cylinder to permit external air to enter the compressor chamber upon the outstroke of the pistons and closes the opening on the instroke of the pistons. I also provide a novel system for lubricating the pistons by applying a lubricant via internal passageways therein.

FIGURE 1 is a fragmentary side elevation view, part- Patented August 9, 1966 ly in section, of an internal combustion engine constructed in accordance with one form of my invention.

FIGURE 2 is an enlarged sectional view of a portion of one piston in the region of the rings showing one part of the lubricating system therefor.

FIGURES 3 and 4 and, respectivley, end and side elevation views, enlarged, of the compressor chamber intake valve shown in FIG. !1.

FIGURE 5 is a fragmentary enlarged view of the undercut rear piston packing depicted in FIG. 1.

FIGURE 6 is a fragmentary enlarged view of the undercut front piston packing depicted in FIG. 1.

Referring now to FIGURE 1 there is shown my novel internal combustion engine of the free-piston type which embodies the present invention. As in the engine described and claimed in the aforementioned US. Patent 3,129,878, it consists of relatively few main pants. To conserve space and to simplify the explanation, little more than half of the entire engine has been shown since practically all of the structure thereof to the right of the midpoint of the combustion chamber is identical with the structure to the left thereof. One exception is the fuelmetering system which, obviously, is associated only with the intake manifold.

Basically, engine 10 consists of two cylinders 11 and -12 having central narrow portions 11a and 12a respectively which interfit a centrally located combustion block 9. Within the respective cylinders 11 and 12 are located reciprocaitng pistons 13 and 14. The narrow cylinder portions l la and 12a also pass through central openings in substantially identical manifolds 15 and 17 and are constructed to mate with or interfit them snugly. While the manifolds 15, 17 are structurally identical, the manifold I15 is used as the air-fuel intake manifold whereas the manifold 17 is used as the exhaust manifold.

There are two end caps at opposite ends of the cylinders, only one of which, end cap '19 is shown in this figure. A number of bolts 211, 22 are provided which may extend the entire length of the engine, passing through aligned apertures in the end caps and in the manifolds. Tension is provided by screwing nuts 16 at the ends of the long bolts thereby urging the end caps and the cylinders toward one another at the center so that the narrow portions l laand 12a tightly intenfit the combustion block openings. Nuts 18 are provided around the bolts 21 and 22 to urge the manifolds 15 and 17 outward so that their stepped central apertures snugly mate with similarly stepped outer surfaces of the cylinder portions 11a and 12a.

The end caps are provided with apertures such as aperture 19a which are located substantially centrally therein and through which is passed a bolt such as the bolt 23. The bolt 23 is connected to an elongated member 2-4 which has a square or other uncircular crosssection designed to fit a similarly cross-sectioned passageway 13a formed within the piston 13. It is the function of this member 24 and this passageway 13a to prevent rotation of the piston 13 about its longitudinal axis and thus, prevent the piston ring joint from snagging in the intake or exhaust ports.

-In accordance with one feature of my invention, it will be .noted that the frictional force produced by the reciprocation of the pistons 13 and 14 is reduced byproviding undercut portions 13b and 1 3c in the piston 13,

- and similar undercut portions in the piston 14 of which only the portion is shown in FIG. 1.

It is characteristic of internal combustion engines that the frictional drag per unit area of rubbing surface generated by the various pistons differs due to differences in the clearance between the piston and cylinder, differences in the actual viscosity of the oil in the clearance (due to temperature differences, differences in accumulations of combustion by-products, etc.), etc. The total frictional force acting on each piston is the product of the area of contact and the frictional drag per unit area. Thus, to reduce the difference in frictional force between the pistons, so as to maintain closer synchronization in the novel free piston engine, the area of contact is minimized by extensive piston undercutting. As described below, this undercut also provides for a very eificient internal air cooling system, and thus, the undercut is very useful with all reciprocating internal combustion engines.

The internal air cooling system consists of applying, via pipe 26, air under pressure into spaces and bounded by part of the inside surface of the portion 11a and 12a, part of the outside surface of the narrow diameter portions 130 and 140 of the piston 13 and 14, the inner end portion of the pistons which include the rings, and the novel compressor inlet valve 28. This air circulates around in the spaces 13c and 140 and is exhausted from the space 130 by means of the tube 31 and its counterpart (not shown) for the space 140. This cooling air may also be blown into the intake and exhaust manifolds. The pressurized air eliminates from the engine any combustion products that may leak past the rings.

This direct internal cooling system has a number of advantage over existing external cooling systems. Most known air-cooled engines require large fins, powerful fans, and a considerable amount of sheetmetal work in order to direct the cooling air around the exterior of the engine. Since the cooling is not directed to the point at which cooling is most needed, i.e., in the region where the piston rubs against the inner wall surface of the cylinder, these conventional systems are relatively inefiicient. Thus, if it is desired to keep the maximum internal engine temperature at about 400 Fahrenheit, for example, a 200 temperature drop through the cylinder and fins must be allowed for, and it is necessary to keep the external fins less than 200".

Using my direct cooling system, however there is no need for large fins, fans, or extensive sheetmetal work since all that is necessary is to provide an inlet for the air through a hole in the cylinder wall which communicates with the portion of the piston which has been undercut to reduce frictional losses. Since the cooling air of my system is applied directly to the surfaces that need to be cooled, the cooling air may undergo a temperature rise to 400 F. Under typical conditions, the external system cooling air may undergo a temperature rise from 70 to 200 (difference of 130), while the internal system cooling air may undergo a temperature rise from 70 to 400 (difference of 330). Assuming that the quantity of heat transferred is equal in both cases, the amount of air required for the external cooling system is 93 or about 2 /2 times the amount of air required by the internal cooling system. Additionally, the movement of the piston provides beneficial turbulence to the cooling air of the internal system.

Fuel metering system This pressurized air cooling system also plays a part in providing in my novel engine an automatic fuel metering system which is responsive to the stroke of the piston 13. To the extent that the outward movement of the piston 13 causes the portion 13g thereof to cover, partially or entirely, the aperture 11b in the cylinder wall, pressure will build up in the tube 26, in the tube 32 and, via a constricting valve 33, in the duct 34 and the bellows 35. The bellows 35 is mechanically coupled by a rigid link 36 to a fuel valve 37 to which fuel is applied via tube 38.

The valve 33 smooths out the pressure applied in pulses to the bellows 35 to a mean value. The valve 37 and the link 36 are so arranged that an increase in the pressure within the bellows 35 will move the link 36 in a direction such as to decrease the amount of fuel applied via the intake manifold 15 to the combustion chamber, and vice versa. In the intervals when the aperture 11b is not covered by the portion 13g, the pressure in tube 32 will be low relative to the pressure in bellows 35, and thus, air will flow from the bellows reducing the pressure therein.

As an example of its operation let it be assumed that the normal outstroke of the piston should be such that portion 13g covers one-half of the aperture III) at its end. This would cause the average pressure in bellows 35 to be of some value, say 20 lbs. per square inch. If the outstroke exceeds this length it will cause perhaps three-quarters of the aperture 11b to be covered so that pneumatic pulses of greater duration and amplitude are applied to bellows 35 increasing its average pressure to, say 21 pounds per square inch. This will move link 36 outward to decrease the fuel applied. Consequently, when the rebouncing pistons come together for the next combustion of fuel, there will be a smaller explosion so that the pistons will not travel outward so far. Hence, the piston portion 13g during the next few strokes will cover less than three-quarters of the aperture. If the outstroke, on the other hand, is less than normal it will cause perhaps one-quarter of the aperture 11b to be covered so that pneumatic pulses of shorter duration and amplitude are applied to bellows 35 thereby decreasing the average pressure therein to 19 pounds per square inch. This will cause the link 36 to move inwardly and increase the fuel rate whereupon the subsequent stronger explosions in the combustion chamber 8 will tend to lengthen the outstroke until it tends, on the average, t cover the predetermined half of the aperture.

Of course, other predetermined average outstroke positions may be effected by changing the location of the aperture 11b, employing a different bellows, changing the pressure of the applied air, etc. The successful operation of this outstroke control system also assumes that the piston will not ordinarily move so far out that its inner face will pass, totally or partially, the aperture 11b.

Compressor valve Another novel feature of my engine, which is described and claimed in my US. Patent 3,175,584, issued Mar. 30, 1965, is my provision of a one piece, highly efficient compressor chamber valve 28 shown magnified in FIGURES 3 and 4. Instead of being operated by a pressure difference, it is designed for much more efiicient mechanical actuation. Valve 28 has a serrated lip 28a having cuts 28c therein. This lip is compressed to enable it to slip into the groove 11c formed in the inner wall of narrow cylinder portion 11a whereupon it resiliently expands to its normal shape. The lip 28a is locked into the groove by the undercut portion 13c of the piston. The inside diameter of the valve is made to have a sliding or frictional fit around the undercut portion of the piston so that the valve will be moved inwardly and outwardly to a limited extent by the reciprocating piston. However, when the valve movement is limited, it will remain stationary and the piston will then slide against the valve. The valve inward movement is limited by the annular flange portion 23b bearing against an inside surface of the compressor chamber 40 and its outward movement is limited by the lip 28a contacting the left vertical side of the groove 110.

On the outstroke of the piston the valve is moved away from the compressor wall 40a by the piston, thereby uncovering the inlet ports 42. This allows air to be drawn into the compressor chamber. As the piston continues to move outward it slides against the valve which remains motionless since it is constrained by the groove 11c.

When the piston starts to move inwardly, the valve 28 moves with it until the valve seats against the wall 40a thereby sealing the sixteen inlet ports 42. For the remainder of the in-stroke the valve stays motionless in its sealing position, while the piston slides against it.

This valve also acts as a flange packing which tends to prevent fuel-air mixture, exhaust products, cooling air, and blow-by combustion products from entering the compressor chamber 40. The valve 28 may be made from glass-filled Teflon.

Lubrication system In order to minimize the friction and wear of the pistons and cylinders I have devised a novel lubrication system which applies oil to the ring area of the pistons by means of an internal passageway within the piston itself. Thus, pistons 13 and 14 have internal passageways 13d and 140! respectively. Connected to the passageway 13d toward the back of the piston is a rigid L-shaped tubular member 44 to which a flexible tubular member 45 is connected. The other end of the flexible member 45 is connected to another rigid tubular member 46 which is screwed or otherwise secured within an L-shaped passageway 47. Of course, an opening at other points along the cylinder wall could alternatively be used as the inlet for the oil.

Oil is applied to the passageway 47 by means of the duct 48. As shown in the enlarged view in FIGURE 2, the inner end of the passageway 13d has an L-shaped portion 13e which opens out into a circular groove 13] that is formed in the outside surface of the piston head 13g. This groove allows the oil to distribute itself evenly around the piston head. Most of the oil tends to be trapped in the region adjacent to the groove by the rings 13h on each side of the groove, assuring an adequate and continuous supply of oil for the rings and cylinder Walls. A small amount of the oil may succeed in getting between the other rubbing surfaces of the piston and the adjacent interior cylinder walls.

Though not shown in FIG. 2, the region of the piston head between the first ring (closest to the combustion chamber) and the combustion chamber is preferably undercut sufiiciently to produce a clearance between it and the adjacent inner cylinder wall. This is done since oil in the groove 13 generally does not reach the surface portion 13m. The duct 31 also acts as an oil drain and as an outlet for pressurized air from the cooling system. In addition, oil drains may also be formed within the manifolds and 17.

Seals, packing, etc.

In order to cushion the end caps against impact by the pistons if the engine goes out of control, shock absorbers such as the absorber 48 may be fastened to the piston guidance members such as the member 24 as shown.

The absorber 48 may be made of rubber or other suitable material.

A rear piston packing member 51 (FIG. 5) is provided which is pressed firmly inward by the annular threaded retaining member 52 that is screwed onto an intermediate threaded portion of the piston 13. Packing 51 has an undercut portion 51a that insures a good seal in the region of portion 51b by effectively increasing the force per unit area of the outer edge of portion 51b against the cylinder 11. Packing 51 has an annular recessed portion 51c which also aids in maintaining the portion 51b in intimate contact with the inside cylinder wall. This assists in isolating the rebounce chamber 41 from the compression or pump chamber 40.

A front piston packing member 50 (FIG. 6) is also provided which is screwed by screws 50d into the Wider diameter portion of the piston. In order to provide a tight seal at the edge of portion 50b it also has an undercut portion 50a. It also includes an annular recess 500 which, by virtue of the air pressure in it, helps to increase the pressure of the seal at 50b against the cylinder wall. By keeping these parts in intimate contact with one another the compression chamber is kept isolated from the rebounce chamber. This front packing also has a portion 502 shaped to act as a shock absorber should the engine go out of control. Both of the packings 50 and 51 may be of Teflon or other materials having similar properties.

While these seals are useful in many types of reciprocating piston engines, they are especially useful in the engine illustrated which employs the pneumatic synchronizing system to be briefly described below.

Synchronizing system As this system is not part of this invention and is shown only as part of one illustrative environment for my invention only a passing reference will be made thereto. Connected to each rebounce chamber is a duct such as duct which passes through an aperture in the end cap 19. The duct is connected to a source (not shown) of a gas under pressure. A restriction such as a needle valve 69 is included along the duct. There is also a vent 61 which is located in the cylinder wall approximately where the outer end of the piston 13 will be when it is near its maximum inward position.

As explained in detail in my U.S. Patent 3,127,881 issued on Apr. 7, 1964, if the piston 13 begins to move inward too far at the end of its instroke, the outer edge of the packing 51 will pass over the inner opening of the passageway 61. Thus, to the extent that the internal opening of the passageway 61 is uncovered by the length of the inward stroke, the pressure in the rebounce chamber 41 (which is being continuously built up by the flow of gas through orifice 68) will be reduced. This occurs because the passageway 61 communicates via the duct 62, the valve 63 and the pipe 64 with a gas receiver which may be, for example, the ambient atmosphere. As a result of this pressure reduction in the rebounce chamber, the piston 13 will tend to have its instrokes in the next several cycles shortened with the result that the inner opening of the passageway 61 will not be exposed so much by the passage of the piston 13 past it. Consequently the pressure in the rebounce chamber 41 will continue to build up uninterruptedly resulting, after a. time, in a tendency toward longer instrokes of the piston. Thus, over a period of time, the average position of the pistons will be stabilized by the synchronizing system just explained. For most elfeotive operation of this system it is evident that the piston seals must be very good to prevent undesired leakage of the pressurized gas from the rebounce chamber.

Miscellaneous remarks In the particular engine shown in FIG. 1 but not constituting part of my engine is a starting system which consists of a substantially cylindrical cavity 65 formed in the combustion block 9. This cavity communicates with the combustion chamber itself by means of a passageway 66. A plug 67 is screwed into and out of the threaded aperture 65a to enable a starting explosive charge to be inserted into the cavity 65 and then, when the plug is screwed in, to channel the explosion into the combustion chamber 8 via the passageway 66. The plug 67 is provided with a longitudinal passageway into which a pin (not shown) may be fitted. Part of the pin protrudes outside the plug 67 and its other end is arranged to strike the charge so as to detonate it when the external end of the pin is struck sharply. The detonation of the charge produces a sudden expansion of the gases through the passageway 66 into the combustion chamber with a force suflicient to cause the pistons 13 and 14 to be immediately forced outward against the pressure in the rebounce chambers. The rebounce pressure will force the pistons inward toward one another thereby compressing the fuel and air mixture applied to the rebounce chamber through the inlet pipe 15a via the manifold 15. This compression will inaugurate the second and successive combustions of the fuel-air charge in the combustion chamber. The combustion chamber block 9 is U preferably provided with annular fins 9a to help dissipate the heat generated within the combustion chamber.

I claim:

1. In an internal combustion engine a dual-purpose system comprising:

(a) a selected number of cylinders each of which has an inside surface against which a piston rubs during movement of said piston therein,

(b) a selected number of pistons each of which is arranged for reciprocal movement in one of said cylinders, each of said pistons having a predetermined part of lesser breadth than other parts thereof as measured in a direction substantially transverse to the direction of movement thereof, said predetermined part being spaced appreciably from said cylinder inner surface so as to form a clearance, said other parts having an outer surface in intimate contact with said inner surface, said pistons having respective strokes which are subject to variation during operation of said engine,

(c) means for applying pressurized gaseous material to said clearance, the pressure of said gaseous material in said applying means being a function of the extent to which said other parts obstruct said applying means, and

(d) utilization means coupled to said applying means and being responsive to changes in the pressure of said gaseous material in said applying means.

2. The dual-purpose system according to claim 1 wherein said utilization means meters the flow of fuel to said engine as a function of the pressure in said applying means.

3. The dual-purpose system according to claim 1 wherein said clearance is intermediate and bounded by said other parts, wherein said applying means includes an aperture through a wall of said cylinder which communicates with said clearance, and wherein at least one of said other parts at times will obstruct said aperture depending upon the extent of the outward stroke of said piston.

4. The dual-purpose system according to claim 3 wherein said applying means also includes a source of said gaseous material under pressure, a first duct coupling said source to said aperture, and wherein said utilization means includes means for applying fuel to said engine, valve means for controlling the amount of fuel passing through said fuel-applying means, a second duct coupled to said first duct, and pressure responsive means coupled to said second duct and to said valve means for operating said valve means in response to the pressure in said second duct.

5. The dual-purpose system according to claim 2 wherein said gaseous material cools said engine in the vicinity of said clearance.

6. The system according to claim 5 wherein means are provided in the wall of said cylinder to permit escape of said gaseous material from said clearance.

References Cited by the Examiner UNITED STATES PATENTS 2,497,781 2/1950 Logashkin 123--41.35 3,076,440 2/1963 Arnold 12341.35

FOREIGN PATENTS 170,909 11/1921 Great Britain.

KARL J. ALBRECHT, Primary Examiner. 

1. IN AN INTERNAL COMBUSTION ENGINE A DUAL-PURPOSE SYSTEM COMPRISING: (A) A SELECTED NUMBER OF CYLINDERS EACH OF WHICH HAS AN INSIDE SURFACE AGAINST WHICH A PISTON RUBS DURING MOVEMENT OF SAID PISTON THEREIN, (B) A SELECTED NUMBER OF PISTONS EACH OF WHICH IS ARRANGED FOR RECIPROCAL MOVEMENT IN ONE OF SAID CYLINDERS, EACH OF SAID PISTONS HAVING A PREDETERMINED PART OF LESSER BREADTH THAN OTHER PARTS THEREOF AS MEASURED IN A DIRECTION SUBSTANTIALLY TRANSVERSE TO THE DIRECTION OF MOVEMENT THEREOF, SAID PREDETERMINED PART BEING SPACED APPRECIABLY FROM SAID CYLINDER INNER SURFACE SO AS TO FORM A CLEARANCE, SAID OTHER PARTS HAVING AN OUTER SURFACE IN INTIMATE CONTACT WITH SAID INNER SURFACE, SAID PISTONS HAVING RESPECTIVE STROKES WHICH ARE SUBJECT TO VARIATION DURING OPERATION OF SAID ENGINE, (C) MEANS FOR APPLYING PRESSURIZED GASEOUS MATERIAL TO SAID CLEARANCE, THE PRESSURE OF SAID GASEOUS MATERIAL IN SAID APPLYING MEANS BEING A FUNCTION OF THE EXTENT TO WHICH SAID OTHER PARTS OBSTRUCT SAID APPLYING MEANS, AND 